我喜欢这样的代码:

function getClientIP() {

    if (isset($_SERVER)) {

        if (isset($_SERVER["HTTP_X_FORWARDED_FOR"]))
            return $_SERVER["HTTP_X_FORWARDED_FOR"];

        if (isset($_SERVER["HTTP_CLIENT_IP"]))
            return $_SERVER["HTTP_CLIENT_IP"];

        return $_SERVER["REMOTE_ADDR"];
    }

    if (getenv('HTTP_X_FORWARDED_FOR'))
        return getenv('HTTP_X_FORWARDED_FOR');

    if (getenv('HTTP_CLIENT_IP'))
        return getenv('HTTP_CLIENT_IP');

    return getenv('REMOTE_ADDR');
}

答案是使用$_SERVER变量。例如，$_SERVER["REMOTE_ADDR"]将返回客户端的IP地址。

你可以使用下面的函数

function get_client_ip() {
    $ipaddress = '';
    if (isset($_SERVER['HTTP_CLIENT_IP']))
        $ipaddress = $_SERVER['HTTP_CLIENT_IP'];
    else if(isset($_SERVER['HTTP_X_FORWARDED_FOR']))
        $ipaddress = $_SERVER['HTTP_X_FORWARDED_FOR'];
    else if(isset($_SERVER['HTTP_X_FORWARDED']))
        $ipaddress = $_SERVER['HTTP_X_FORWARDED'];
    else if(isset($_SERVER['HTTP_FORWARDED_FOR']))
        $ipaddress = $_SERVER['HTTP_FORWARDED_FOR'];
    else if(isset($_SERVER['HTTP_FORWARDED']))
        $ipaddress = $_SERVER['HTTP_FORWARDED'];
    else if(isset($_SERVER['REMOTE_ADDR']))
        $ipaddress = $_SERVER['REMOTE_ADDR'];
    else
        $ipaddress = 'UNKNOWN';
    return $ipaddress;
}

echo $_SERVER['REMOTE_ADDR'];

http://php.net/manual/en/reserved.variables.server.php

这里有一个简单的一行代码

$ip = $_SERVER['HTTP_X_FORWARDED_FOR']?: $_SERVER['HTTP_CLIENT_IP']?: $_SERVER['REMOTE_ADDR'];

编辑:

上面的代码可能会返回保留地址(如10.0.0.1)，所有代理服务器的地址列表，等等。 要处理这些情况，请使用以下代码:

function valid_ip($ip) {
    // for list of reserved IP addresses, see https://en.wikipedia.org/wiki/Reserved_IP_addresses
    return $ip && substr($ip, 0, 4) != '127.' && substr($ip, 0, 4) != '127.' && substr($ip, 0, 3) != '10.' && substr($ip, 0, 2) != '0.' ? $ip : false;
}

function get_client_ip() {
    // using explode to get only client ip from list of forwarders. see https://en.wikipedia.org/wiki/X-Forwarded-For
    return
    @$_SERVER['HTTP_X_FORWARDED_FOR'] ? explode(',', $_SERVER['HTTP_X_FORWARDED_FOR'], 2)[0] :
    @$_SERVER['HTTP_CLIENT_IP'] ? explode(',', $_SERVER['HTTP_CLIENT_IP'], 2)[0] :
    valid_ip(@$_SERVER['REMOTE_ADDR']) ?:
    'UNKNOWN';
}

echo get_client_ip();

试试这个:

 $_SERVER['REMOTE_ADDR'];